The evolution of man : a popular exposition of the principal points of human ontogeny and phylogeny . , single cells of the primary germ-layers as-sumed the character of egg-cells, others that of fertilizingseed-cells. (Cf. Chapter XXV.) This hypothesis is foundedon the fact that sexual reproduction is yet met with in thesame simple forms in the lowest Plant-Animals (Zoophyta),especially in the Sponges. Two small animal forms are especially interesting intheir bearing on tliis aspect of the Gastraea theory. Theyhave as yet been little observed, but of all extant animalsthey are most nearly all
The evolution of man : a popular exposition of the principal points of human ontogeny and phylogeny . , single cells of the primary germ-layers as-sumed the character of egg-cells, others that of fertilizingseed-cells. (Cf. Chapter XXV.) This hypothesis is foundedon the fact that sexual reproduction is yet met with in thesame simple forms in the lowest Plant-Animals (Zoophyta),especially in the Sponges. Two small animal forms are especially interesting intheir bearing on tliis aspect of the Gastraea theory. Theyhave as yet been little observed, but of all extant animalsthey are most nearly allied to the primaeval Gastraea, andmay therefore be called the Gastraeads of the One of these animals, Haliphysema (Figs. 180 and181), has been described by Bowerbank as a Sponge; theother, Gastrophysema, by Carter as a Rhizopod (as Squa-mulina ). The entire mature body of the developed person EXTANT GASTIL5SADS. 6/ of Haliphysema forms a most simple, cylindrical or egg-shaped pouch, the wall of which consists of two cavity of the pouch is the stomach-cavity, and the.
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